Author
Topic: Cummins ISL 350 (Read 1846 times)

I have an ISL 350 that has 95000 miles is useing a about a pint of coolant in about 3000 miles since 65000 miles.No sign of any external leaks. Engine oil looks normal. Everything operates as it has since I bought it with 5000 miles in 2010. Coolant has been changed 5000 miles ago for the third time since 2010.

Loss of coolant, pint of fluid loss in 3000 miles is nothing to worry about. Possible causeradiator pressure cap opening at wrong value or incorrect pressure cap. Note little hose just below radiator cap running along side of the radiator ( check to see if it is wet on endof hose on inside ) if answer is yes that is where you are loosing coolant. You will note,The end of hose is wet but not leaving any taletail signs of fluid leaking on ground. CouldLoose a little radiator fluid on Long steep grades via of over heating or getting hot for short while and venting through little hose just under filler cap.@. Dave Atherton Retired Catmechanic.

Though the systems are more complex, testing for a leak is basically the same as in a car.

Pressurize the system to two PSI over the cap rating and watch for pressure drop/coolant leak.

If this happens more in cold weather, consider replacing regular hose clamps, particularly on the larger-diameter hoses with CONSTANT TORQUE CLAMPS. They compensate for the contraction/expansion of the metal. Adding a second clamp is another pretty inexpensive option.

As Dave said, may just be a weak pressure cap allowing coolant to escape. Put a zip lock bag over the end of the overflow hose to see if that is where it is coming from.

Also, some coaches are fit with an overflow reservoir. With the proper radiator cap, they allow for the expansion of the coolant when hot and return the coolant to the radiator/cooling system when cold (just like in most other vehicles). If your coach has one, verify that it is not cracked and allowing coolant to escape.